Embryo cryopreservation
Our service entails flushing preimplantation embryos, selecting 225 healthy embryos and freezing them in groups of 25. We use a stepwise slow freezing protocol that maximizes viability.
How many mice are expected from each group of 25 embryos?
We expect that each group of 25 embryos will
yield 10 live born mice. Thus, 200 cryopreserved embryos should provide more
than sufficient backup for a strain or mutant. However, if cryopreserved
embryos will be the only source of this strain or mutant in the world, we
recommend freezing two or three times as many.
How many mice are required to get 225 healthy embryos?
Ten to twenty-five plugged, superovulated females,
depending on strain (assume a plug rate of 75% of superovulated females, so
start with 12 or more females). Since it is unlikely that you will have 10-25
stud males on hand, we will do several matings. Please discuss with us the
strain background of your mice so that we can better inform you how many mice
will be required to get the appropriate number of embryos. With the small number (3 to 5) of stud males which a lab typically has on hand, expect it to take 4 or five months of breeding to obtain and freeze sufficient healthy embryos. Strains with reduced fecundity may take longer.
The stud males must be older than 2 months
of age, and less than a year old. Males should be housed individually for
two weeks prior to mating. If it has been some time since they have mated
or if it is their first time, put a female in their cage 2 weeks before
mating for cryopreservation, and then remove the female one week later.
Females should be 6 to 10 weeks old. We will
administer hormones to superovulate the females.
Superovulation is the forcing of the estrus
cycle through timed injection of hormones, allowing us to synchronize and
schedule matings. Superovulation also can lead to greater numbers of eggs
in some strains.
Alternatives
We can provide cryopreservation of
ovaries and sperm, but these procedures are not recommended for most customers.
What level of confidence can be placed in the frozen samples?
We chose the parameters that we did with the belief
that the typical need of investigators would be for backup of strains or mutants
that are available elsewhere. If your intention is to cryopreserve as the sole
source of a mutant or strain, we recommend that you cryopreserve twice and split
the frozen samples between two liquid nitrogen freezers at two sites.
WHAT YOU WILL PROVIDE PART
An account number.
The mice to be cryopreserved.
WHAT WE WILL PROVIDE
Hormones, hormone injection and mating of the mice to be cryopreserved.
Cryopreservation of 225 embryos in 9 or more straws.